The present invention generally relates to the field of spacecraft that use pulsed plasma thrusters and, more particularly, to how pulsed plasma thrusters are incorporated with the spacecraft.
Pulsed plasma thrusters are known in the spacecraft art and have in fact been flown on missions into outer space. One function of pulsed plasma thrusters is for fine positioning attitude control of spacecraft. These types of pulsed plasma thrusters in the past have been xe2x80x9cbolt-onxe2x80x9d type units that are separately attached to the exterior body of the spacecraft.
The present invention generally relates to how pulsed plasma thrusters may be incorporated with a spacecraft. In a first aspect of the present invention, a spacecraft includes a spacecraft body, a first pulsed plasma thruster (although more than one pulsed plasma thruster may and typically will be utilized), and a first inflatable member that is also interconnected with the body of the spacecraft. Representative examples of the first inflatable member include an inflatable boom or strut. The first inflatable member will typically be stored within the spacecraft body, and typically an appropriate fluid will be directed within the first inflatable member to move the same from its stowed position to its fully deployed position. One way of interconnecting the first inflatable member is by having one end of the first inflatable member be interconnected in some manner with the body of the spacecraft such that its second end it will be spaced from the spacecraft body when the first inflatable member is deployed. The first inflatable member also includes a first rigid support structure such as a cap or the like. The first pulsed plasma thruster (and possibly other pulsed plasma thrusters) is disposed at this first rigid support structure.
Various refinements exist of the features noted in relation to the subject first aspect of the present invention. Further features may also be incorporated in the subject first aspect of the present invention as well. These refinements and additional features may exist individually or in any combination. The length of the first rigid support structure may be significantly less than the length of the body of the first inflatable member when deployed. In one embodiment, the ratio of the length of the first rigid support structure to the total length of the first inflatable member when deployed is no more than about 1%. The first rigid support structure with its first pulsed plasma thruster also may be incorporated with the first inflatable member at a variety of locations. In one embodiment, the first rigid support structure is disposed at least substantially at the second or distal end of the first inflatable member, such that the first rigid support structure may be characterized as a first end cap or the like. As such, the first rigid support structure would be disposed in spaced relation to the spacecraft body by a membrane or the like which defines the body of the first inflatable member. Another option would be to dispose the first rigid support structure at some intermediate location between the two extreme ends of the first inflatable member. In this case, a portion of a membrane or the like which defines the body of the first inflatable member would be disposed on both sides of the first rigid support structure. It may also be desirable to include a plurality of first rigid support structures that are spaced along the length of the first inflatable member. One or more pulsed plasma thrusters may be disposed on any number of these first rigid support structures.
A plurality of pulsed plasma thrusters may be interconnected with the first rigid support structure that is interconnected with the first inflatable member. One of these pulsed plasma thrusters may be oriented on the first rigid support structure so as to direct thrust therefrom in a first direction. Another of these pulsed plasma thrusters may be oriented on the first rigid support structure so as to direct its thrust in a second direction which differs from the first direction. Any number and/or orientation of pulsed plasma thrusters may be disposed on the first rigid support structure, subject of course to the size of the first rigid support structure accommodating the desired number of pulsed plasma thrusters.
The subject first aspect may also include a second inflatable member that is similarly configured to the first inflatable member described above. Typically the spacecraft of the subject first aspect will include at least three inflatable members of the type described above in relation to the first inflatable member. These plurality of inflatable members may be utilized to deploy a membrane which may provide any number of a variety of functions. For instance, the membrane may be utilized to deploy a one or more solar panels, one or more photovoltaic cells or cell arrays, one or more antenna apertures, one or more solar sail membranes, or one or more occulting membrane. Typically, these membranes will have a surface area of at least about 2,500 m2 in one in embodiment, and about 4,900 m2 in another embodiment.
Spacecraft bus power may be utilized to operate or xe2x80x9cfirexe2x80x9d the first pulsed plasma thruster at the desired/required time. The spacecraft bus would typically be located at the body of the spacecraft. A number of options may be employed in relation to how this power is delivered from the spacecraft bus to the pulsed plasma thruster(s) disposed on the first rigid support structure. One option would be to provide a high voltage power supply, a high voltage storage capacitor, and controller for each pulsed plasma thruster that is disposed on the first rigid support structure associated with the first inflatable member. The high voltage power supply, high voltage storage capacitor, and controller all may be disposed on the first rigid support structure associated with the first inflatable member. A series connection of the above-noted components and in the above-noted order may be utilized, with the spacecraft bus and the high voltage power supply being interconnected by a flexible circuit which extends between the spacecraft bus and the first rigid support structure along the inflatable member in some manner for electrical interconnection with each of the high voltage power supplies at the first rigid support structure This flexible circuit may be attached to a membrane which defines the body of the first inflatable member, or alternatively may extend along the first inflatable member within its hollow interior after the first inflatable member has been inflated/expanded.
Another option for providing power from the spacecraft bus to the plasma pulsed thruster(s) that are disposed on the first rigid support structure associated with the first inflatable member is to dispose a high voltage power supply at the body of the spacecraft and to electrically interconnect the same with the spacecraft bus. A high voltage storage capacitor and controller may be provided for each pulsed plasma thruster that is disposed on the first rigid support structure. The high voltage storage capacitor and controller of each pulsed plasma thruster that is disposed on the first rigid support structure may be located at the first rigid support structure as well, may be connected in series in the above-noted order, and further may be electrically interconnected with the high voltage power supply by the above-noted type of flexible circuit which would then extend between the high voltage power supply and the first rigid support structure, where appropriate electrical connections could then be made with each of the pulsed plasma thrusters disposed on the first rigid support structure through the noted components.
Yet another option which may be employed for delivering power from the spacecraft bus to the pulsed plasma thruster(s) disposed on the first rigid support structure of the first inflatable member is to dispose a single low voltage storage device at the first rigid support structure and to electrically interconnect the same with the spacecraft bus by the above-noted type of flexible circuit. This single low voltage storage device may direct power to a separate high voltage power supply, high voltage storage capacitor, and controller for each pulsed plasma thruster that is disposed on the first rigid support structure associated with the first inflatable member. The high voltage power supply, high voltage storage capacitor, and controller of each pulsed plasma thruster all may be disposed on the first rigid structure and may be interconnected in series in the noted order.
A second aspect of the present invention is directed to a spacecraft which includes a spacecraft body. An exterior surface of this spacecraft body may be defined as a first surface. A first recess is disposed on this first surface, and a first pulsed plasma thruster is disposed within this first recess and is appropriately interconnected with the spacecraft body.
Various refinements exist of the features noted in relation to the subject second aspect of the present invention. Further features may also be incorporated in the subject second aspect of the present invention as well. These refinements and additional features may exist individually or in any combination. One advantage which may be realized by the subject second aspect of the present invention is that incorporating pulsed plasma thrusters on the spacecraft body need not necessarily increase the amount of space that is taken up by the spacecraft body. In this regard and in one embodiment, preferably no portion of any pulsed plasma thruster disposed within the first recess associated with the second aspect extends beyond those portions of the first surface of the spacecraft body which are disposed about the perimeter of the first recess. Stated another way, preferably the height of any pulsed plasma thruster disposed within the first recess is no more than the depth of the first recess.
The spacecraft body of the second aspect may be defined by a plurality of rigid panels that are appropriately interconnected. Each of these panels may include first and second sheets with a core disposed therebetween. In this case the first sheet corresponds with the first surface of the spacecraft body (i.e., the first sheet is on the exterior of the spacecraft). This core may be a honeycomb structure or an appropriate foam.
The spacecraft of the second aspect may be what is characterized as a nano-satellite. Typically, the body of a nano-satellite is no more than about 2 m2 in size. Nano-satellites will commonly use the above-noted type construction of first and second sheets with a core disposed therebetween.
Multiple pulsed plasma thrusters may be disposed in the first recess on the exterior surface of the spacecraft body. All or at least part of the pulsed plasma thruster(s) may be disposed in this first recess. At least the plasma-producing material of the pulsed plasma thruster(s) will be disposed within the first recess. Multiple first recesses may be disposed on the spacecraft body in spaced relation, and may include one or more pulsed plasma thrusters in the manner discussed herein.